parser: handle `[noreturn]` on methods too

vlib/v/checker/tests/run/noreturn_method_can_be_used_instead_of_panic.run.out

@@ -0,0 +1 @@
+Test.zz_exit called, as it should

vlib/v/checker/tests/run/noreturn_method_can_be_used_instead_of_panic.vv

@@ -0,0 +1,19 @@
+struct Test {}
+
+[noreturn]
+fn (mut t Test) zz_exit() {
+	println('${@METHOD} called, as it should')
+	flush_stdout()
+	exit(0)
+}
+
+fn optional() ?int {
+	return error('oh no')
+}
+
+fn main() {
+	mut test := Test{}
+	a := optional() or { test.zz_exit() }
+	println(a)
+	exit(1)
+}

vlib/v/parser/fn.v

@@ -399,6 +399,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			generic_names: generic_names
 			is_pub: is_pub
 			is_deprecated: is_deprecated
+			is_noreturn: is_noreturn
 			is_unsafe: is_unsafe
 			is_main: is_main
 			is_test: is_test